1. Field of the Invention
The present invention relates to an inherently stable composite part for screening noise from automobile engines or the like. More particularly, the present invention is related to improved sound deadening plastic composite element with inner packing for an engine hood. Composite parts of this type are used primarily in the automobile industry and in auto bodies, particularly as engine hoods.
The automobile industry is becoming increasingly interested in noise-insulating structural elements and is particularly intent upon incorporating these elements in assembly lines during manufacture of the vehicle.
2. Description of the Prior Art
For this purpose a hood for the engine chamber of a power vehicle is already known from European Patent B-111 430 where the inside of the hood is provided with a sound-absorbing packing. This packing is of suitable material, especially of compressed fiber material, and has rod-like formations which stand up from the hood when this packing is in assembled state. The hollow spaces which thus are formed between packing and hood have a sound-absorbing effect. This packing is self-supporting, i.e., is suitably compacted or compressed, and is heavy. The use of such self-supporting packings leads to undesirably heavy engine hoods and has all of the technical problems which are already known in the assembly phase of vehicle manufacture.
A noise-insulating covering element for the inside of an engine hood is also known from German DE-25 10 607, having several convexities, which together with the engine hood define an air-filled chamber, of which the dimensioning produces optimum acoustic absorption in the low and middle frequency ranges. This covering element is essentially self-supporting and is fastened to reinforcement ribs on the engine hood. Also, this structural part is not assembled until after the vehicle manufacture is completed and requires an undesirably rigid engine hood. For the security of the vehicle occupants, however, the goal oil the modern vehicle industry is to construct the nose and rear parts as deformable wrinkle zones, i.e., with a variable rigidity corresponding to the expected forces.
Additional elements being attached thereto, for instance for sound insulation, thus require increased rigidity of the outside sheet and lead to undesirable higher weight.